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use std::cell::{Cell, RefCell};
use std::cmp::max;
use std::iter;
use std::ops::Deref;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::HirId;
use rustc_hir_analysis::autoderef::{self, Autoderef};
use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
use rustc_infer::infer::{self, DefineOpaqueTypes, InferOk, TyCtxtInferExt};
use rustc_infer::traits::ObligationCauseCode;
use rustc_middle::middle::stability;
use rustc_middle::query::Providers;
use rustc_middle::ty::fast_reject::{simplify_type, TreatParams};
use rustc_middle::ty::{
self, AssocItem, AssocItemContainer, GenericArgs, GenericArgsRef, GenericParamDefKind,
ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt, Upcast,
};
use rustc_middle::{bug, span_bug};
use rustc_session::lint;
use rustc_span::def_id::{DefId, LocalDefId};
use rustc_span::edit_distance::{
edit_distance_with_substrings, find_best_match_for_name_with_substrings,
};
use rustc_span::symbol::{sym, Ident};
use rustc_span::{Span, Symbol, DUMMY_SP};
use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
use rustc_trait_selection::traits::query::method_autoderef::{
CandidateStep, MethodAutoderefBadTy, MethodAutoderefStepsResult,
};
use rustc_trait_selection::traits::query::CanonicalTyGoal;
use rustc_trait_selection::traits::{self, ObligationCause, ObligationCtxt};
use smallvec::{smallvec, SmallVec};
use tracing::{debug, instrument};
use self::CandidateKind::*;
pub(crate) use self::PickKind::*;
use super::{suggest, CandidateSource, MethodError, NoMatchData};
use crate::FnCtxt;
/// Boolean flag used to indicate if this search is for a suggestion
/// or not. If true, we can allow ambiguity and so forth.
#[derive(Clone, Copy, Debug)]
pub(crate) struct IsSuggestion(pub bool);
pub(crate) struct ProbeContext<'a, 'tcx> {
fcx: &'a FnCtxt<'a, 'tcx>,
span: Span,
mode: Mode,
method_name: Option<Ident>,
return_type: Option<Ty<'tcx>>,
/// This is the OriginalQueryValues for the steps queries
/// that are answered in steps.
orig_steps_var_values: &'a OriginalQueryValues<'tcx>,
steps: &'tcx [CandidateStep<'tcx>],
inherent_candidates: Vec<Candidate<'tcx>>,
extension_candidates: Vec<Candidate<'tcx>>,
impl_dups: FxHashSet<DefId>,
/// When probing for names, include names that are close to the
/// requested name (by edit distance)
allow_similar_names: bool,
/// List of potential private candidates. Will be trimmed to ones that
/// actually apply and then the result inserted into `private_candidate`
private_candidates: Vec<Candidate<'tcx>>,
/// Some(candidate) if there is a private candidate
private_candidate: Cell<Option<(DefKind, DefId)>>,
/// Collects near misses when the candidate functions are missing a `self` keyword and is only
/// used for error reporting
static_candidates: RefCell<Vec<CandidateSource>>,
/// Collects near misses when trait bounds for type parameters are unsatisfied and is only used
/// for error reporting
unsatisfied_predicates: RefCell<
Vec<(ty::Predicate<'tcx>, Option<ty::Predicate<'tcx>>, Option<ObligationCause<'tcx>>)>,
>,
scope_expr_id: HirId,
/// Is this probe being done for a diagnostic? This will skip some error reporting
/// machinery, since we don't particularly care about, for example, similarly named
/// candidates if we're *reporting* similarly named candidates.
is_suggestion: IsSuggestion,
}
impl<'a, 'tcx> Deref for ProbeContext<'a, 'tcx> {
type Target = FnCtxt<'a, 'tcx>;
fn deref(&self) -> &Self::Target {
self.fcx
}
}
#[derive(Debug, Clone)]
pub(crate) struct Candidate<'tcx> {
pub(crate) item: ty::AssocItem,
pub(crate) kind: CandidateKind<'tcx>,
pub(crate) import_ids: SmallVec<[LocalDefId; 1]>,
}
#[derive(Debug, Clone)]
pub(crate) enum CandidateKind<'tcx> {
InherentImplCandidate(DefId),
ObjectCandidate(ty::PolyTraitRef<'tcx>),
TraitCandidate(ty::PolyTraitRef<'tcx>),
WhereClauseCandidate(ty::PolyTraitRef<'tcx>),
}
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
enum ProbeResult {
NoMatch,
BadReturnType,
Match,
}
/// When adjusting a receiver we often want to do one of
///
/// - Add a `&` (or `&mut`), converting the receiver from `T` to `&T` (or `&mut T`)
/// - If the receiver has type `*mut T`, convert it to `*const T`
///
/// This type tells us which one to do.
///
/// Note that in principle we could do both at the same time. For example, when the receiver has
/// type `T`, we could autoref it to `&T`, then convert to `*const T`. Or, when it has type `*mut
/// T`, we could convert it to `*const T`, then autoref to `&*const T`. However, currently we do
/// (at most) one of these. Either the receiver has type `T` and we convert it to `&T` (or with
/// `mut`), or it has type `*mut T` and we convert it to `*const T`.
#[derive(Debug, PartialEq, Copy, Clone)]
pub(crate) enum AutorefOrPtrAdjustment {
/// Receiver has type `T`, add `&` or `&mut` (it `T` is `mut`), and maybe also "unsize" it.
/// Unsizing is used to convert a `[T; N]` to `[T]`, which only makes sense when autorefing.
Autoref {
mutbl: hir::Mutability,
/// Indicates that the source expression should be "unsized" to a target type.
/// This is special-cased for just arrays unsizing to slices.
unsize: bool,
},
/// Receiver has type `*mut T`, convert to `*const T`
ToConstPtr,
}
impl AutorefOrPtrAdjustment {
fn get_unsize(&self) -> bool {
match self {
AutorefOrPtrAdjustment::Autoref { mutbl: _, unsize } => *unsize,
AutorefOrPtrAdjustment::ToConstPtr => false,
}
}
}
#[derive(Debug, Clone)]
pub(crate) struct Pick<'tcx> {
pub item: ty::AssocItem,
pub kind: PickKind<'tcx>,
pub import_ids: SmallVec<[LocalDefId; 1]>,
/// Indicates that the source expression should be autoderef'd N times
/// ```ignore (not-rust)
/// A = expr | *expr | **expr | ...
/// ```
pub autoderefs: usize,
/// Indicates that we want to add an autoref (and maybe also unsize it), or if the receiver is
/// `*mut T`, convert it to `*const T`.
pub autoref_or_ptr_adjustment: Option<AutorefOrPtrAdjustment>,
pub self_ty: Ty<'tcx>,
/// Unstable candidates alongside the stable ones.
unstable_candidates: Vec<(Candidate<'tcx>, Symbol)>,
}
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum PickKind<'tcx> {
InherentImplPick,
ObjectPick,
TraitPick,
WhereClausePick(
// Trait
ty::PolyTraitRef<'tcx>,
),
}
pub(crate) type PickResult<'tcx> = Result<Pick<'tcx>, MethodError<'tcx>>;
#[derive(PartialEq, Eq, Copy, Clone, Debug)]
pub(crate) enum Mode {
// An expression of the form `receiver.method_name(...)`.
// Autoderefs are performed on `receiver`, lookup is done based on the
// `self` argument of the method, and static methods aren't considered.
MethodCall,
// An expression of the form `Type::item` or `<T>::item`.
// No autoderefs are performed, lookup is done based on the type each
// implementation is for, and static methods are included.
Path,
}
#[derive(PartialEq, Eq, Copy, Clone, Debug)]
pub(crate) enum ProbeScope {
// Single candidate coming from pre-resolved delegation method.
Single(DefId),
// Assemble candidates coming only from traits in scope.
TraitsInScope,
// Assemble candidates coming from all traits.
AllTraits,
}
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
/// This is used to offer suggestions to users. It returns methods
/// that could have been called which have the desired return
/// type. Some effort is made to rule out methods that, if called,
/// would result in an error (basically, the same criteria we
/// would use to decide if a method is a plausible fit for
/// ambiguity purposes).
#[instrument(level = "debug", skip(self, candidate_filter))]
pub fn probe_for_return_type_for_diagnostic(
&self,
span: Span,
mode: Mode,
return_type: Ty<'tcx>,
self_ty: Ty<'tcx>,
scope_expr_id: HirId,
candidate_filter: impl Fn(&ty::AssocItem) -> bool,
) -> Vec<ty::AssocItem> {
let method_names = self
.probe_op(
span,
mode,
None,
Some(return_type),
IsSuggestion(true),
self_ty,
scope_expr_id,
ProbeScope::AllTraits,
|probe_cx| Ok(probe_cx.candidate_method_names(candidate_filter)),
)
.unwrap_or_default();
method_names
.iter()
.flat_map(|&method_name| {
self.probe_op(
span,
mode,
Some(method_name),
Some(return_type),
IsSuggestion(true),
self_ty,
scope_expr_id,
ProbeScope::AllTraits,
|probe_cx| probe_cx.pick(),
)
.ok()
.map(|pick| pick.item)
})
.collect()
}
#[instrument(level = "debug", skip(self))]
pub fn probe_for_name(
&self,
mode: Mode,
item_name: Ident,
return_type: Option<Ty<'tcx>>,
is_suggestion: IsSuggestion,
self_ty: Ty<'tcx>,
scope_expr_id: HirId,
scope: ProbeScope,
) -> PickResult<'tcx> {
self.probe_op(
item_name.span,
mode,
Some(item_name),
return_type,
is_suggestion,
self_ty,
scope_expr_id,
scope,
|probe_cx| probe_cx.pick(),
)
}
#[instrument(level = "debug", skip(self))]
pub(crate) fn probe_for_name_many(
&self,
mode: Mode,
item_name: Ident,
return_type: Option<Ty<'tcx>>,
is_suggestion: IsSuggestion,
self_ty: Ty<'tcx>,
scope_expr_id: HirId,
scope: ProbeScope,
) -> Result<Vec<Candidate<'tcx>>, MethodError<'tcx>> {
self.probe_op(
item_name.span,
mode,
Some(item_name),
return_type,
is_suggestion,
self_ty,
scope_expr_id,
scope,
|probe_cx| {
Ok(probe_cx
.inherent_candidates
.into_iter()
.chain(probe_cx.extension_candidates)
.collect())
},
)
}
pub(crate) fn probe_op<OP, R>(
&'a self,
span: Span,
mode: Mode,
method_name: Option<Ident>,
return_type: Option<Ty<'tcx>>,
is_suggestion: IsSuggestion,
self_ty: Ty<'tcx>,
scope_expr_id: HirId,
scope: ProbeScope,
op: OP,
) -> Result<R, MethodError<'tcx>>
where
OP: FnOnce(ProbeContext<'_, 'tcx>) -> Result<R, MethodError<'tcx>>,
{
let mut orig_values = OriginalQueryValues::default();
let param_env_and_self_ty = self.canonicalize_query(
ParamEnvAnd { param_env: self.param_env, value: self_ty },
&mut orig_values,
);
let steps = match mode {
Mode::MethodCall => self.tcx.method_autoderef_steps(param_env_and_self_ty),
Mode::Path => self.probe(|_| {
// Mode::Path - the deref steps is "trivial". This turns
// our CanonicalQuery into a "trivial" QueryResponse. This
// is a bit inefficient, but I don't think that writing
// special handling for this "trivial case" is a good idea.
let infcx = &self.infcx;
let (ParamEnvAnd { param_env: _, value: self_ty }, canonical_inference_vars) =
infcx.instantiate_canonical(span, ¶m_env_and_self_ty);
debug!(
"probe_op: Mode::Path, param_env_and_self_ty={:?} self_ty={:?}",
param_env_and_self_ty, self_ty
);
MethodAutoderefStepsResult {
steps: infcx.tcx.arena.alloc_from_iter([CandidateStep {
self_ty: self.make_query_response_ignoring_pending_obligations(
canonical_inference_vars,
self_ty,
),
autoderefs: 0,
from_unsafe_deref: false,
unsize: false,
}]),
opt_bad_ty: None,
reached_recursion_limit: false,
}
}),
};
// If our autoderef loop had reached the recursion limit,
// report an overflow error, but continue going on with
// the truncated autoderef list.
if steps.reached_recursion_limit {
self.probe(|_| {
let ty = &steps
.steps
.last()
.unwrap_or_else(|| span_bug!(span, "reached the recursion limit in 0 steps?"))
.self_ty;
let ty = self
.probe_instantiate_query_response(span, &orig_values, ty)
.unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
autoderef::report_autoderef_recursion_limit_error(self.tcx, span, ty.value);
});
}
// If we encountered an `_` type or an error type during autoderef, this is
// ambiguous.
if let Some(bad_ty) = &steps.opt_bad_ty {
if is_suggestion.0 {
// Ambiguity was encountered during a suggestion. There's really
// not much use in suggesting methods in this case.
return Err(MethodError::NoMatch(NoMatchData {
static_candidates: Vec::new(),
unsatisfied_predicates: Vec::new(),
out_of_scope_traits: Vec::new(),
similar_candidate: None,
mode,
}));
} else if bad_ty.reached_raw_pointer
&& !self.tcx.features().arbitrary_self_types
&& !self.tcx.sess.at_least_rust_2018()
{
// this case used to be allowed by the compiler,
// so we do a future-compat lint here for the 2015 edition
// (see https://github.com/rust-lang/rust/issues/46906)
self.tcx.node_span_lint(
lint::builtin::TYVAR_BEHIND_RAW_POINTER,
scope_expr_id,
span,
|lint| {
lint.primary_message("type annotations needed");
},
);
} else {
// Ended up encountering a type variable when doing autoderef,
// but it may not be a type variable after processing obligations
// in our local `FnCtxt`, so don't call `structurally_resolve_type`.
let ty = &bad_ty.ty;
let ty = self
.probe_instantiate_query_response(span, &orig_values, ty)
.unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
let ty = self.resolve_vars_if_possible(ty.value);
let guar = match *ty.kind() {
ty::Infer(ty::TyVar(_)) => {
let raw_ptr_call =
bad_ty.reached_raw_pointer && !self.tcx.features().arbitrary_self_types;
let mut err = self.err_ctxt().emit_inference_failure_err(
self.body_id,
span,
ty.into(),
TypeAnnotationNeeded::E0282,
!raw_ptr_call,
);
if raw_ptr_call {
err.span_label(span, "cannot call a method on a raw pointer with an unknown pointee type");
}
err.emit()
}
ty::Error(guar) => guar,
_ => bug!("unexpected bad final type in method autoderef"),
};
self.demand_eqtype(span, ty, Ty::new_error(self.tcx, guar));
return Err(MethodError::NoMatch(NoMatchData {
static_candidates: Vec::new(),
unsatisfied_predicates: Vec::new(),
out_of_scope_traits: Vec::new(),
similar_candidate: None,
mode,
}));
}
}
debug!("ProbeContext: steps for self_ty={:?} are {:?}", self_ty, steps);
// this creates one big transaction so that all type variables etc
// that we create during the probe process are removed later
self.probe(|_| {
let mut probe_cx = ProbeContext::new(
self,
span,
mode,
method_name,
return_type,
&orig_values,
steps.steps,
scope_expr_id,
is_suggestion,
);
match scope {
ProbeScope::TraitsInScope => {
probe_cx.assemble_inherent_candidates();
probe_cx.assemble_extension_candidates_for_traits_in_scope();
}
ProbeScope::AllTraits => {
probe_cx.assemble_inherent_candidates();
probe_cx.assemble_extension_candidates_for_all_traits();
}
ProbeScope::Single(def_id) => {
let item = self.tcx.associated_item(def_id);
// FIXME(fn_delegation): Delegation to inherent methods is not yet supported.
assert_eq!(item.container, AssocItemContainer::TraitContainer);
let trait_def_id = self.tcx.parent(def_id);
let trait_span = self.tcx.def_span(trait_def_id);
let trait_args = self.fresh_args_for_item(trait_span, trait_def_id);
let trait_ref = ty::TraitRef::new_from_args(self.tcx, trait_def_id, trait_args);
probe_cx.push_candidate(
Candidate {
item,
kind: CandidateKind::TraitCandidate(ty::Binder::dummy(trait_ref)),
import_ids: smallvec![],
},
false,
);
}
};
op(probe_cx)
})
}
}
pub(crate) fn provide(providers: &mut Providers) {
providers.method_autoderef_steps = method_autoderef_steps;
}
fn method_autoderef_steps<'tcx>(
tcx: TyCtxt<'tcx>,
goal: CanonicalTyGoal<'tcx>,
) -> MethodAutoderefStepsResult<'tcx> {
debug!("method_autoderef_steps({:?})", goal);
let (ref infcx, goal, inference_vars) = tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &goal);
let ParamEnvAnd { param_env, value: self_ty } = goal;
let mut autoderef =
Autoderef::new(infcx, param_env, hir::def_id::CRATE_DEF_ID, DUMMY_SP, self_ty)
.include_raw_pointers()
.silence_errors();
let mut reached_raw_pointer = false;
let mut steps: Vec<_> = autoderef
.by_ref()
.map(|(ty, d)| {
let step = CandidateStep {
self_ty: infcx.make_query_response_ignoring_pending_obligations(inference_vars, ty),
autoderefs: d,
from_unsafe_deref: reached_raw_pointer,
unsize: false,
};
if let ty::RawPtr(_, _) = ty.kind() {
// all the subsequent steps will be from_unsafe_deref
reached_raw_pointer = true;
}
step
})
.collect();
let final_ty = autoderef.final_ty(true);
let opt_bad_ty = match final_ty.kind() {
ty::Infer(ty::TyVar(_)) | ty::Error(_) => Some(MethodAutoderefBadTy {
reached_raw_pointer,
ty: infcx.make_query_response_ignoring_pending_obligations(inference_vars, final_ty),
}),
ty::Array(elem_ty, _) => {
let dereferences = steps.len() - 1;
steps.push(CandidateStep {
self_ty: infcx.make_query_response_ignoring_pending_obligations(
inference_vars,
Ty::new_slice(infcx.tcx, *elem_ty),
),
autoderefs: dereferences,
// this could be from an unsafe deref if we had
// a *mut/const [T; N]
from_unsafe_deref: reached_raw_pointer,
unsize: true,
});
None
}
_ => None,
};
debug!("method_autoderef_steps: steps={:?} opt_bad_ty={:?}", steps, opt_bad_ty);
MethodAutoderefStepsResult {
steps: tcx.arena.alloc_from_iter(steps),
opt_bad_ty: opt_bad_ty.map(|ty| &*tcx.arena.alloc(ty)),
reached_recursion_limit: autoderef.reached_recursion_limit(),
}
}
impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
fn new(
fcx: &'a FnCtxt<'a, 'tcx>,
span: Span,
mode: Mode,
method_name: Option<Ident>,
return_type: Option<Ty<'tcx>>,
orig_steps_var_values: &'a OriginalQueryValues<'tcx>,
steps: &'tcx [CandidateStep<'tcx>],
scope_expr_id: HirId,
is_suggestion: IsSuggestion,
) -> ProbeContext<'a, 'tcx> {
ProbeContext {
fcx,
span,
mode,
method_name,
return_type,
inherent_candidates: Vec::new(),
extension_candidates: Vec::new(),
impl_dups: FxHashSet::default(),
orig_steps_var_values,
steps,
allow_similar_names: false,
private_candidates: Vec::new(),
private_candidate: Cell::new(None),
static_candidates: RefCell::new(Vec::new()),
unsatisfied_predicates: RefCell::new(Vec::new()),
scope_expr_id,
is_suggestion,
}
}
fn reset(&mut self) {
self.inherent_candidates.clear();
self.extension_candidates.clear();
self.impl_dups.clear();
self.private_candidates.clear();
self.private_candidate.set(None);
self.static_candidates.borrow_mut().clear();
self.unsatisfied_predicates.borrow_mut().clear();
}
///////////////////////////////////////////////////////////////////////////
// CANDIDATE ASSEMBLY
fn push_candidate(&mut self, candidate: Candidate<'tcx>, is_inherent: bool) {
let is_accessible = if let Some(name) = self.method_name {
let item = candidate.item;
let hir_id = self.tcx.local_def_id_to_hir_id(self.body_id);
let def_scope =
self.tcx.adjust_ident_and_get_scope(name, item.container_id(self.tcx), hir_id).1;
item.visibility(self.tcx).is_accessible_from(def_scope, self.tcx)
} else {
true
};
if is_accessible {
if is_inherent {
self.inherent_candidates.push(candidate);
} else {
self.extension_candidates.push(candidate);
}
} else {
self.private_candidates.push(candidate);
}
}
fn assemble_inherent_candidates(&mut self) {
for step in self.steps.iter() {
self.assemble_probe(&step.self_ty);
}
}
#[instrument(level = "debug", skip(self))]
fn assemble_probe(&mut self, self_ty: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>) {
let raw_self_ty = self_ty.value.value;
match *raw_self_ty.kind() {
ty::Dynamic(data, ..) if let Some(p) = data.principal() => {
// Subtle: we can't use `instantiate_query_response` here: using it will
// commit to all of the type equalities assumed by inference going through
// autoderef (see the `method-probe-no-guessing` test).
//
// However, in this code, it is OK if we end up with an object type that is
// "more general" than the object type that we are evaluating. For *every*
// object type `MY_OBJECT`, a function call that goes through a trait-ref
// of the form `<MY_OBJECT as SuperTraitOf(MY_OBJECT)>::func` is a valid
// `ObjectCandidate`, and it should be discoverable "exactly" through one
// of the iterations in the autoderef loop, so there is no problem with it
// being discoverable in another one of these iterations.
//
// Using `instantiate_canonical` on our
// `Canonical<QueryResponse<Ty<'tcx>>>` and then *throwing away* the
// `CanonicalVarValues` will exactly give us such a generalization - it
// will still match the original object type, but it won't pollute our
// type variables in any form, so just do that!
let (QueryResponse { value: generalized_self_ty, .. }, _ignored_var_values) =
self.fcx.instantiate_canonical(self.span, self_ty);
self.assemble_inherent_candidates_from_object(generalized_self_ty);
self.assemble_inherent_impl_candidates_for_type(p.def_id());
if self.tcx.has_attr(p.def_id(), sym::rustc_has_incoherent_inherent_impls) {
self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty);
}
}
ty::Adt(def, _) => {
let def_id = def.did();
self.assemble_inherent_impl_candidates_for_type(def_id);
if self.tcx.has_attr(def_id, sym::rustc_has_incoherent_inherent_impls) {
self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty);
}
}
ty::Foreign(did) => {
self.assemble_inherent_impl_candidates_for_type(did);
if self.tcx.has_attr(did, sym::rustc_has_incoherent_inherent_impls) {
self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty);
}
}
ty::Param(p) => {
self.assemble_inherent_candidates_from_param(p);
}
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Str
| ty::Array(..)
| ty::Slice(_)
| ty::RawPtr(_, _)
| ty::Ref(..)
| ty::Never
| ty::Tuple(..) => self.assemble_inherent_candidates_for_incoherent_ty(raw_self_ty),
_ => {}
}
}
fn assemble_inherent_candidates_for_incoherent_ty(&mut self, self_ty: Ty<'tcx>) {
let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::AsCandidateKey) else {
bug!("unexpected incoherent type: {:?}", self_ty)
};
for &impl_def_id in self.tcx.incoherent_impls(simp).into_iter().flatten() {
self.assemble_inherent_impl_probe(impl_def_id);
}
}
fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) {
let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id).into_iter().flatten();
for &impl_def_id in impl_def_ids {
self.assemble_inherent_impl_probe(impl_def_id);
}
}
#[instrument(level = "debug", skip(self))]
fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId) {
if !self.impl_dups.insert(impl_def_id) {
return; // already visited
}
for item in self.impl_or_trait_item(impl_def_id) {
if !self.has_applicable_self(&item) {
// No receiver declared. Not a candidate.
self.record_static_candidate(CandidateSource::Impl(impl_def_id));
continue;
}
self.push_candidate(
Candidate {
item,
kind: InherentImplCandidate(impl_def_id),
import_ids: smallvec![],
},
true,
);
}
}
#[instrument(level = "debug", skip(self))]
fn assemble_inherent_candidates_from_object(&mut self, self_ty: Ty<'tcx>) {
let principal = match self_ty.kind() {
ty::Dynamic(ref data, ..) => Some(data),
_ => None,
}
.and_then(|data| data.principal())
.unwrap_or_else(|| {
span_bug!(
self.span,
"non-object {:?} in assemble_inherent_candidates_from_object",
self_ty
)
});
// It is illegal to invoke a method on a trait instance that refers to
// the `Self` type. An [`ObjectSafetyViolation::SupertraitSelf`] error
// will be reported by `object_safety.rs` if the method refers to the
// `Self` type anywhere other than the receiver. Here, we use a
// instantiation that replaces `Self` with the object type itself. Hence,
// a `&self` method will wind up with an argument type like `&dyn Trait`.
let trait_ref = principal.with_self_ty(self.tcx, self_ty);
self.assemble_candidates_for_bounds(
traits::supertraits(self.tcx, trait_ref),
|this, new_trait_ref, item| {
this.push_candidate(
Candidate {
item,
kind: ObjectCandidate(new_trait_ref),
import_ids: smallvec![],
},
true,
);
},
);
}
#[instrument(level = "debug", skip(self))]
fn assemble_inherent_candidates_from_param(&mut self, param_ty: ty::ParamTy) {
let bounds = self.param_env.caller_bounds().iter().filter_map(|predicate| {
let bound_predicate = predicate.kind();
match bound_predicate.skip_binder() {
ty::ClauseKind::Trait(trait_predicate) => {
match *trait_predicate.trait_ref.self_ty().kind() {
ty::Param(p) if p == param_ty => {
Some(bound_predicate.rebind(trait_predicate.trait_ref))
}
_ => None,
}
}
ty::ClauseKind::RegionOutlives(_)
| ty::ClauseKind::TypeOutlives(_)
| ty::ClauseKind::Projection(_)
| ty::ClauseKind::ConstArgHasType(_, _)
| ty::ClauseKind::WellFormed(_)
| ty::ClauseKind::ConstEvaluatable(_) => None,
}
});
self.assemble_candidates_for_bounds(bounds, |this, poly_trait_ref, item| {
this.push_candidate(
Candidate {
item,
kind: WhereClauseCandidate(poly_trait_ref),
import_ids: smallvec![],
},
true,
);
});
}
// Do a search through a list of bounds, using a callback to actually
// create the candidates.
fn assemble_candidates_for_bounds<F>(
&mut self,
bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
mut mk_cand: F,
) where
F: for<'b> FnMut(&mut ProbeContext<'b, 'tcx>, ty::PolyTraitRef<'tcx>, ty::AssocItem),
{
for bound_trait_ref in bounds {
debug!("elaborate_bounds(bound_trait_ref={:?})", bound_trait_ref);
for item in self.impl_or_trait_item(bound_trait_ref.def_id()) {
if !self.has_applicable_self(&item) {
self.record_static_candidate(CandidateSource::Trait(bound_trait_ref.def_id()));
} else {
mk_cand(self, bound_trait_ref, item);
}
}
}
}
#[instrument(level = "debug", skip(self))]
fn assemble_extension_candidates_for_traits_in_scope(&mut self) {
let mut duplicates = FxHashSet::default();
let opt_applicable_traits = self.tcx.in_scope_traits(self.scope_expr_id);
if let Some(applicable_traits) = opt_applicable_traits {
for trait_candidate in applicable_traits.iter() {
let trait_did = trait_candidate.def_id;
if duplicates.insert(trait_did) {
self.assemble_extension_candidates_for_trait(
&trait_candidate.import_ids,
trait_did,
);
}
}
}
}
#[instrument(level = "debug", skip(self))]
fn assemble_extension_candidates_for_all_traits(&mut self) {
let mut duplicates = FxHashSet::default();
for trait_info in suggest::all_traits(self.tcx) {
if duplicates.insert(trait_info.def_id) {
self.assemble_extension_candidates_for_trait(&smallvec![], trait_info.def_id);
}
}
}
fn matches_return_type(&self, method: ty::AssocItem, expected: Ty<'tcx>) -> bool {
match method.kind {
ty::AssocKind::Fn => self.probe(|_| {
let args = self.fresh_args_for_item(self.span, method.def_id);
let fty = self.tcx.fn_sig(method.def_id).instantiate(self.tcx, args);
let fty = self.instantiate_binder_with_fresh_vars(self.span, infer::FnCall, fty);
self.can_eq(self.param_env, fty.output(), expected)
}),
_ => false,
}
}
#[instrument(level = "debug", skip(self))]
fn assemble_extension_candidates_for_trait(
&mut self,
import_ids: &SmallVec<[LocalDefId; 1]>,
trait_def_id: DefId,
) {
let trait_args = self.fresh_args_for_item(self.span, trait_def_id);
let trait_ref = ty::TraitRef::new_from_args(self.tcx, trait_def_id, trait_args);
if self.tcx.is_trait_alias(trait_def_id) {
// For trait aliases, recursively assume all explicitly named traits are relevant
for expansion in traits::expand_trait_aliases(
self.tcx,
iter::once((ty::Binder::dummy(trait_ref), self.span)),
) {
let bound_trait_ref = expansion.trait_ref();
for item in self.impl_or_trait_item(bound_trait_ref.def_id()) {
if !self.has_applicable_self(&item) {
self.record_static_candidate(CandidateSource::Trait(
bound_trait_ref.def_id(),
));
} else {
self.push_candidate(
Candidate {
item,
import_ids: import_ids.clone(),
kind: TraitCandidate(bound_trait_ref),
},
false,
);
}
}
}
} else {
debug_assert!(self.tcx.is_trait(trait_def_id));
if self.tcx.trait_is_auto(trait_def_id) {
return;
}
for item in self.impl_or_trait_item(trait_def_id) {
// Check whether `trait_def_id` defines a method with suitable name.
if !self.has_applicable_self(&item) {
debug!("method has inapplicable self");
self.record_static_candidate(CandidateSource::Trait(trait_def_id));
continue;
}
self.push_candidate(
Candidate {
item,
import_ids: import_ids.clone(),
kind: TraitCandidate(ty::Binder::dummy(trait_ref)),
},
false,
);
}
}
}
fn candidate_method_names(
&self,
candidate_filter: impl Fn(&ty::AssocItem) -> bool,
) -> Vec<Ident> {
let mut set = FxHashSet::default();
let mut names: Vec<_> = self
.inherent_candidates
.iter()
.chain(&self.extension_candidates)
.filter(|candidate| candidate_filter(&candidate.item))
.filter(|candidate| {
if let Some(return_ty) = self.return_type {
self.matches_return_type(candidate.item, return_ty)
} else {
true
}
})
// ensure that we don't suggest unstable methods
.filter(|candidate| {
// note that `DUMMY_SP` is ok here because it is only used for
// suggestions and macro stuff which isn't applicable here.
!matches!(
self.tcx.eval_stability(candidate.item.def_id, None, DUMMY_SP, None),
stability::EvalResult::Deny { .. }
)
})
.map(|candidate| candidate.item.ident(self.tcx))
.filter(|&name| set.insert(name))
.collect();
// Sort them by the name so we have a stable result.
names.sort_by(|a, b| a.as_str().cmp(b.as_str()));
names
}
///////////////////////////////////////////////////////////////////////////
// THE ACTUAL SEARCH
#[instrument(level = "debug", skip(self))]
fn pick(mut self) -> PickResult<'tcx> {
assert!(self.method_name.is_some());
if let Some(r) = self.pick_core() {
return r;
}
// If it's a `lookup_probe_for_diagnostic`, then quit early. No need to
// probe for other candidates.
if self.is_suggestion.0 {
return Err(MethodError::NoMatch(NoMatchData {
static_candidates: vec![],
unsatisfied_predicates: vec![],
out_of_scope_traits: vec![],
similar_candidate: None,
mode: self.mode,
}));
}
debug!("pick: actual search failed, assemble diagnostics");
let static_candidates = std::mem::take(self.static_candidates.get_mut());
let private_candidate = self.private_candidate.take();
let unsatisfied_predicates = std::mem::take(self.unsatisfied_predicates.get_mut());
// things failed, so lets look at all traits, for diagnostic purposes now:
self.reset();
let span = self.span;
let tcx = self.tcx;
self.assemble_extension_candidates_for_all_traits();
let out_of_scope_traits = match self.pick_core() {
Some(Ok(p)) => vec![p.item.container_id(self.tcx)],
Some(Err(MethodError::Ambiguity(v))) => v
.into_iter()
.map(|source| match source {
CandidateSource::Trait(id) => id,
CandidateSource::Impl(impl_id) => match tcx.trait_id_of_impl(impl_id) {
Some(id) => id,
None => span_bug!(span, "found inherent method when looking at traits"),
},
})
.collect(),
Some(Err(MethodError::NoMatch(NoMatchData {
out_of_scope_traits: others, ..
}))) => {
assert!(others.is_empty());
vec![]
}
_ => vec![],
};
if let Some((kind, def_id)) = private_candidate {
return Err(MethodError::PrivateMatch(kind, def_id, out_of_scope_traits));
}
let similar_candidate = self.probe_for_similar_candidate()?;
Err(MethodError::NoMatch(NoMatchData {
static_candidates,
unsatisfied_predicates,
out_of_scope_traits,
similar_candidate,
mode: self.mode,
}))
}
fn pick_core(&self) -> Option<PickResult<'tcx>> {
// Pick stable methods only first, and consider unstable candidates if not found.
self.pick_all_method(Some(&mut vec![])).or_else(|| self.pick_all_method(None))
}
fn pick_all_method(
&self,
mut unstable_candidates: Option<&mut Vec<(Candidate<'tcx>, Symbol)>>,
) -> Option<PickResult<'tcx>> {
self.steps
.iter()
.filter(|step| {
debug!("pick_all_method: step={:?}", step);
// skip types that are from a type error or that would require dereferencing
// a raw pointer
!step.self_ty.references_error() && !step.from_unsafe_deref
})
.find_map(|step| {
let InferOk { value: self_ty, obligations: _ } = self
.fcx
.probe_instantiate_query_response(
self.span,
self.orig_steps_var_values,
&step.self_ty,
)
.unwrap_or_else(|_| {
span_bug!(self.span, "{:?} was applicable but now isn't?", step.self_ty)
});
self.pick_by_value_method(step, self_ty, unstable_candidates.as_deref_mut())
.or_else(|| {
self.pick_autorefd_method(
step,
self_ty,
hir::Mutability::Not,
unstable_candidates.as_deref_mut(),
)
.or_else(|| {
self.pick_autorefd_method(
step,
self_ty,
hir::Mutability::Mut,
unstable_candidates.as_deref_mut(),
)
})
.or_else(|| {
self.pick_const_ptr_method(
step,
self_ty,
unstable_candidates.as_deref_mut(),
)
})
})
})
}
/// For each type `T` in the step list, this attempts to find a method where
/// the (transformed) self type is exactly `T`. We do however do one
/// transformation on the adjustment: if we are passing a region pointer in,
/// we will potentially *reborrow* it to a shorter lifetime. This allows us
/// to transparently pass `&mut` pointers, in particular, without consuming
/// them for their entire lifetime.
fn pick_by_value_method(
&self,
step: &CandidateStep<'tcx>,
self_ty: Ty<'tcx>,
unstable_candidates: Option<&mut Vec<(Candidate<'tcx>, Symbol)>>,
) -> Option<PickResult<'tcx>> {
if step.unsize {
return None;
}
self.pick_method(self_ty, unstable_candidates).map(|r| {
r.map(|mut pick| {
pick.autoderefs = step.autoderefs;
// Insert a `&*` or `&mut *` if this is a reference type:
if let ty::Ref(_, _, mutbl) = *step.self_ty.value.value.kind() {
pick.autoderefs += 1;
pick.autoref_or_ptr_adjustment = Some(AutorefOrPtrAdjustment::Autoref {
mutbl,
unsize: pick.autoref_or_ptr_adjustment.is_some_and(|a| a.get_unsize()),
})
}
pick
})
})
}
fn pick_autorefd_method(
&self,
step: &CandidateStep<'tcx>,
self_ty: Ty<'tcx>,
mutbl: hir::Mutability,
unstable_candidates: Option<&mut Vec<(Candidate<'tcx>, Symbol)>>,
) -> Option<PickResult<'tcx>> {
let tcx = self.tcx;
// In general, during probing we erase regions.
let region = tcx.lifetimes.re_erased;
let autoref_ty = Ty::new_ref(tcx, region, self_ty, mutbl);
self.pick_method(autoref_ty, unstable_candidates).map(|r| {
r.map(|mut pick| {
pick.autoderefs = step.autoderefs;
pick.autoref_or_ptr_adjustment =
Some(AutorefOrPtrAdjustment::Autoref { mutbl, unsize: step.unsize });
pick
})
})
}
/// If `self_ty` is `*mut T` then this picks `*const T` methods. The reason why we have a
/// special case for this is because going from `*mut T` to `*const T` with autoderefs and
/// autorefs would require dereferencing the pointer, which is not safe.
fn pick_const_ptr_method(
&self,
step: &CandidateStep<'tcx>,
self_ty: Ty<'tcx>,
unstable_candidates: Option<&mut Vec<(Candidate<'tcx>, Symbol)>>,
) -> Option<PickResult<'tcx>> {
// Don't convert an unsized reference to ptr
if step.unsize {
return None;
}
let &ty::RawPtr(ty, hir::Mutability::Mut) = self_ty.kind() else {
return None;
};
let const_ptr_ty = Ty::new_imm_ptr(self.tcx, ty);
self.pick_method(const_ptr_ty, unstable_candidates).map(|r| {
r.map(|mut pick| {
pick.autoderefs = step.autoderefs;
pick.autoref_or_ptr_adjustment = Some(AutorefOrPtrAdjustment::ToConstPtr);
pick
})
})
}
fn pick_method(
&self,
self_ty: Ty<'tcx>,
mut unstable_candidates: Option<&mut Vec<(Candidate<'tcx>, Symbol)>>,
) -> Option<PickResult<'tcx>> {
debug!("pick_method(self_ty={})", self.ty_to_string(self_ty));
let mut possibly_unsatisfied_predicates = Vec::new();
for (kind, candidates) in
[("inherent", &self.inherent_candidates), ("extension", &self.extension_candidates)]
{
debug!("searching {} candidates", kind);
let res = self.consider_candidates(
self_ty,
candidates,
&mut possibly_unsatisfied_predicates,
unstable_candidates.as_deref_mut(),
);
if let Some(pick) = res {
return Some(pick);
}
}
if self.private_candidate.get().is_none() {
if let Some(Ok(pick)) =
self.consider_candidates(self_ty, &self.private_candidates, &mut vec![], None)
{
self.private_candidate.set(Some((pick.item.kind.as_def_kind(), pick.item.def_id)));
}
}
// `pick_method` may be called twice for the same self_ty if no stable methods
// match. Only extend once.
if unstable_candidates.is_some() {
self.unsatisfied_predicates.borrow_mut().extend(possibly_unsatisfied_predicates);
}
None
}
fn consider_candidates(
&self,
self_ty: Ty<'tcx>,
candidates: &[Candidate<'tcx>],
possibly_unsatisfied_predicates: &mut Vec<(
ty::Predicate<'tcx>,
Option<ty::Predicate<'tcx>>,
Option<ObligationCause<'tcx>>,
)>,
mut unstable_candidates: Option<&mut Vec<(Candidate<'tcx>, Symbol)>>,
) -> Option<PickResult<'tcx>> {
let mut applicable_candidates: Vec<_> = candidates
.iter()
.map(|probe| {
(probe, self.consider_probe(self_ty, probe, possibly_unsatisfied_predicates))
})
.filter(|&(_, status)| status != ProbeResult::NoMatch)
.collect();
debug!("applicable_candidates: {:?}", applicable_candidates);
if applicable_candidates.len() > 1 {
if let Some(pick) =
self.collapse_candidates_to_trait_pick(self_ty, &applicable_candidates)
{
return Some(Ok(pick));
}
}
if let Some(uc) = &mut unstable_candidates {
applicable_candidates.retain(|&(candidate, _)| {
if let stability::EvalResult::Deny { feature, .. } =
self.tcx.eval_stability(candidate.item.def_id, None, self.span, None)
{
uc.push((candidate.clone(), feature));
return false;
}
true
});
}
if applicable_candidates.len() > 1 {
let sources = candidates.iter().map(|p| self.candidate_source(p, self_ty)).collect();
return Some(Err(MethodError::Ambiguity(sources)));
}
applicable_candidates.pop().map(|(probe, status)| match status {
ProbeResult::Match => {
Ok(probe
.to_unadjusted_pick(self_ty, unstable_candidates.cloned().unwrap_or_default()))
}
ProbeResult::NoMatch | ProbeResult::BadReturnType => Err(MethodError::BadReturnType),
})
}
}
impl<'tcx> Pick<'tcx> {
/// In case there were unstable name collisions, emit them as a lint.
/// Checks whether two picks do not refer to the same trait item for the same `Self` type.
/// Only useful for comparisons of picks in order to improve diagnostics.
/// Do not use for type checking.
pub(crate) fn differs_from(&self, other: &Self) -> bool {
let Self {
item:
AssocItem {
def_id,
name: _,
kind: _,
container: _,
trait_item_def_id: _,
fn_has_self_parameter: _,
opt_rpitit_info: _,
is_effects_desugaring: _,
},
kind: _,
import_ids: _,
autoderefs: _,
autoref_or_ptr_adjustment: _,
self_ty,
unstable_candidates: _,
} = *self;
self_ty != other.self_ty || def_id != other.item.def_id
}
/// In case there were unstable name collisions, emit them as a lint.
pub(crate) fn maybe_emit_unstable_name_collision_hint(
&self,
tcx: TyCtxt<'tcx>,
span: Span,
scope_expr_id: HirId,
) {
if self.unstable_candidates.is_empty() {
return;
}
let def_kind = self.item.kind.as_def_kind();
tcx.node_span_lint(lint::builtin::UNSTABLE_NAME_COLLISIONS, scope_expr_id, span, |lint| {
lint.primary_message(format!(
"{} {} with this name may be added to the standard library in the future",
tcx.def_kind_descr_article(def_kind, self.item.def_id),
tcx.def_kind_descr(def_kind, self.item.def_id),
));
match (self.item.kind, self.item.container) {
(ty::AssocKind::Fn, _) => {
// FIXME: This should be a `span_suggestion` instead of `help`
// However `self.span` only
// highlights the method name, so we can't use it. Also consider reusing
// the code from `report_method_error()`.
lint.help(format!(
"call with fully qualified syntax `{}(...)` to keep using the current \
method",
tcx.def_path_str(self.item.def_id),
));
}
(ty::AssocKind::Const, ty::AssocItemContainer::TraitContainer) => {
let def_id = self.item.container_id(tcx);
lint.span_suggestion(
span,
"use the fully qualified path to the associated const",
format!(
"<{} as {}>::{}",
self.self_ty,
tcx.def_path_str(def_id),
self.item.name
),
Applicability::MachineApplicable,
);
}
_ => {}
}
tcx.disabled_nightly_features(
lint,
Some(scope_expr_id),
self.unstable_candidates.iter().map(|(candidate, feature)| {
(format!(" `{}`", tcx.def_path_str(candidate.item.def_id)), *feature)
}),
);
});
}
}
impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
fn select_trait_candidate(
&self,
trait_ref: ty::TraitRef<'tcx>,
) -> traits::SelectionResult<'tcx, traits::Selection<'tcx>> {
let cause = traits::ObligationCause::misc(self.span, self.body_id);
let obligation = traits::Obligation::new(self.tcx, cause, self.param_env, trait_ref);
traits::SelectionContext::new(self).select(&obligation)
}
/// Used for ambiguous method call error reporting. Uses probing that throws away the result internally,
/// so do not use to make a decision that may lead to a successful compilation.
fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>) -> CandidateSource {
match candidate.kind {
InherentImplCandidate(_) => {
CandidateSource::Impl(candidate.item.container_id(self.tcx))
}
ObjectCandidate(_) | WhereClauseCandidate(_) => {
CandidateSource::Trait(candidate.item.container_id(self.tcx))
}
TraitCandidate(trait_ref) => self.probe(|_| {
let trait_ref =
self.instantiate_binder_with_fresh_vars(self.span, infer::FnCall, trait_ref);
let (xform_self_ty, _) =
self.xform_self_ty(candidate.item, trait_ref.self_ty(), trait_ref.args);
// Guide the trait selection to show impls that have methods whose type matches
// up with the `self` parameter of the method.
let _ = self.at(&ObligationCause::dummy(), self.param_env).sup(
DefineOpaqueTypes::Yes,
xform_self_ty,
self_ty,
);
match self.select_trait_candidate(trait_ref) {
Ok(Some(traits::ImplSource::UserDefined(ref impl_data))) => {
// If only a single impl matches, make the error message point
// to that impl.
CandidateSource::Impl(impl_data.impl_def_id)
}
_ => CandidateSource::Trait(candidate.item.container_id(self.tcx)),
}
}),
}
}
#[instrument(level = "trace", skip(self, possibly_unsatisfied_predicates), ret)]
fn consider_probe(
&self,
self_ty: Ty<'tcx>,
probe: &Candidate<'tcx>,
possibly_unsatisfied_predicates: &mut Vec<(
ty::Predicate<'tcx>,
Option<ty::Predicate<'tcx>>,
Option<ObligationCause<'tcx>>,
)>,
) -> ProbeResult {
debug!("consider_probe: self_ty={:?} probe={:?}", self_ty, probe);
self.probe(|snapshot| {
let outer_universe = self.universe();
let mut result = ProbeResult::Match;
let cause = &self.misc(self.span);
let ocx = ObligationCtxt::new_with_diagnostics(self);
let mut trait_predicate = None;
let (mut xform_self_ty, mut xform_ret_ty);
match probe.kind {
InherentImplCandidate(impl_def_id) => {
let impl_args = self.fresh_args_for_item(self.span, impl_def_id);
let impl_ty = self.tcx.type_of(impl_def_id).instantiate(self.tcx, impl_args);
(xform_self_ty, xform_ret_ty) =
self.xform_self_ty(probe.item, impl_ty, impl_args);
xform_self_ty = ocx.normalize(cause, self.param_env, xform_self_ty);
match ocx.sup(cause, self.param_env, xform_self_ty, self_ty) {
Ok(()) => {}
Err(err) => {
debug!("--> cannot relate self-types {:?}", err);
return ProbeResult::NoMatch;
}
}
// FIXME: Weirdly, we normalize the ret ty in this candidate, but no other candidates.
xform_ret_ty = ocx.normalize(cause, self.param_env, xform_ret_ty);
// Check whether the impl imposes obligations we have to worry about.
let impl_def_id = probe.item.container_id(self.tcx);
let impl_bounds =
self.tcx.predicates_of(impl_def_id).instantiate(self.tcx, impl_args);
let impl_bounds = ocx.normalize(cause, self.param_env, impl_bounds);
// Convert the bounds into obligations.
ocx.register_obligations(traits::predicates_for_generics(
|idx, span| {
let code = ObligationCauseCode::WhereClauseInExpr(
impl_def_id,
span,
self.scope_expr_id,
idx,
);
ObligationCause::new(self.span, self.body_id, code)
},
self.param_env,
impl_bounds,
));
}
TraitCandidate(poly_trait_ref) => {
// Some trait methods are excluded for arrays before 2021.
// (`array.into_iter()` wants a slice iterator for compatibility.)
if let Some(method_name) = self.method_name {
if self_ty.is_array() && !method_name.span.at_least_rust_2021() {
let trait_def = self.tcx.trait_def(poly_trait_ref.def_id());
if trait_def.skip_array_during_method_dispatch {
return ProbeResult::NoMatch;
}
}
// Some trait methods are excluded for boxed slices before 2024.
// (`boxed_slice.into_iter()` wants a slice iterator for compatibility.)
if self_ty.is_box()
&& self_ty.boxed_ty().is_slice()
&& !method_name.span.at_least_rust_2024()
{
let trait_def = self.tcx.trait_def(poly_trait_ref.def_id());
if trait_def.skip_boxed_slice_during_method_dispatch {
return ProbeResult::NoMatch;
}
}
}
let trait_ref = self.instantiate_binder_with_fresh_vars(
self.span,
infer::FnCall,
poly_trait_ref,
);
let trait_ref = ocx.normalize(cause, self.param_env, trait_ref);
(xform_self_ty, xform_ret_ty) =
self.xform_self_ty(probe.item, trait_ref.self_ty(), trait_ref.args);
xform_self_ty = ocx.normalize(cause, self.param_env, xform_self_ty);
match self_ty.kind() {
// HACK: opaque types will match anything for which their bounds hold.
// Thus we need to prevent them from trying to match the `&_` autoref
// candidates that get created for `&self` trait methods.
ty::Alias(ty::Opaque, alias_ty)
if self.infcx.can_define_opaque_ty(alias_ty.def_id)
&& !xform_self_ty.is_ty_var() =>
{
return ProbeResult::NoMatch;
}
_ => match ocx.sup(cause, self.param_env, xform_self_ty, self_ty) {
Ok(()) => {}
Err(err) => {
debug!("--> cannot relate self-types {:?}", err);
return ProbeResult::NoMatch;
}
},
}
let obligation = traits::Obligation::new(
self.tcx,
cause.clone(),
self.param_env,
ty::Binder::dummy(trait_ref),
);
// FIXME(-Znext-solver): We only need this hack to deal with fatal
// overflow in the old solver.
if self.infcx.next_trait_solver() || self.infcx.predicate_may_hold(&obligation)
{
ocx.register_obligation(obligation);
} else {
result = ProbeResult::NoMatch;
if let Ok(Some(candidate)) = self.select_trait_candidate(trait_ref) {
for nested_obligation in candidate.nested_obligations() {
if !self.infcx.predicate_may_hold(&nested_obligation) {
possibly_unsatisfied_predicates.push((
self.resolve_vars_if_possible(nested_obligation.predicate),
Some(self.resolve_vars_if_possible(obligation.predicate)),
Some(nested_obligation.cause),
));
}
}
}
}
trait_predicate = Some(trait_ref.upcast(self.tcx));
}
ObjectCandidate(poly_trait_ref) | WhereClauseCandidate(poly_trait_ref) => {
let trait_ref = self.instantiate_binder_with_fresh_vars(
self.span,
infer::FnCall,
poly_trait_ref,
);
(xform_self_ty, xform_ret_ty) =
self.xform_self_ty(probe.item, trait_ref.self_ty(), trait_ref.args);
xform_self_ty = ocx.normalize(cause, self.param_env, xform_self_ty);
match ocx.sup(cause, self.param_env, xform_self_ty, self_ty) {
Ok(()) => {}
Err(err) => {
debug!("--> cannot relate self-types {:?}", err);
return ProbeResult::NoMatch;
}
}
}
}
// Evaluate those obligations to see if they might possibly hold.
for error in ocx.select_where_possible() {
result = ProbeResult::NoMatch;
let nested_predicate = self.resolve_vars_if_possible(error.obligation.predicate);
if let Some(trait_predicate) = trait_predicate
&& nested_predicate == self.resolve_vars_if_possible(trait_predicate)
{
// Don't report possibly unsatisfied predicates if the root
// trait obligation from a `TraitCandidate` is unsatisfied.
// That just means the candidate doesn't hold.
} else {
possibly_unsatisfied_predicates.push((
nested_predicate,
Some(self.resolve_vars_if_possible(error.root_obligation.predicate))
.filter(|root_predicate| *root_predicate != nested_predicate),
Some(error.obligation.cause),
));
}
}
if let ProbeResult::Match = result
&& let Some(return_ty) = self.return_type
&& let Some(mut xform_ret_ty) = xform_ret_ty
{
// `xform_ret_ty` has only been normalized for `InherentImplCandidate`.
// We don't normalize the other candidates for perf/backwards-compat reasons...
// but `self.return_type` is only set on the diagnostic-path, so we
// should be okay doing it here.
if !matches!(probe.kind, InherentImplCandidate(_)) {
xform_ret_ty = ocx.normalize(&cause, self.param_env, xform_ret_ty);
}
debug!("comparing return_ty {:?} with xform ret ty {:?}", return_ty, xform_ret_ty);
match ocx.sup(cause, self.param_env, return_ty, xform_ret_ty) {
Ok(()) => {}
Err(_) => {
result = ProbeResult::BadReturnType;
}
}
// Evaluate those obligations to see if they might possibly hold.
for error in ocx.select_where_possible() {
result = ProbeResult::NoMatch;
possibly_unsatisfied_predicates.push((
error.obligation.predicate,
Some(error.root_obligation.predicate)
.filter(|predicate| *predicate != error.obligation.predicate),
Some(error.root_obligation.cause),
));
}
}
// Previously, method probe used `evaluate_predicate` to determine if a predicate
// was impossible to satisfy. This did a leak check, so we must also do a leak
// check here to prevent backwards-incompatible ambiguity being introduced. See
// `tests/ui/methods/leak-check-disquality.rs` for a simple example of when this
// may happen.
if let Err(_) = self.leak_check(outer_universe, Some(snapshot)) {
result = ProbeResult::NoMatch;
}
result
})
}
/// Sometimes we get in a situation where we have multiple probes that are all impls of the
/// same trait, but we don't know which impl to use. In this case, since in all cases the
/// external interface of the method can be determined from the trait, it's ok not to decide.
/// We can basically just collapse all of the probes for various impls into one where-clause
/// probe. This will result in a pending obligation so when more type-info is available we can
/// make the final decision.
///
/// Example (`tests/ui/method-two-trait-defer-resolution-1.rs`):
///
/// ```ignore (illustrative)
/// trait Foo { ... }
/// impl Foo for Vec<i32> { ... }
/// impl Foo for Vec<usize> { ... }
/// ```
///
/// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
/// use, so it's ok to just commit to "using the method from the trait Foo".
fn collapse_candidates_to_trait_pick(
&self,
self_ty: Ty<'tcx>,
probes: &[(&Candidate<'tcx>, ProbeResult)],
) -> Option<Pick<'tcx>> {
// Do all probes correspond to the same trait?
let container = probes[0].0.item.trait_container(self.tcx)?;
for (p, _) in &probes[1..] {
let p_container = p.item.trait_container(self.tcx)?;
if p_container != container {
return None;
}
}
// FIXME: check the return type here somehow.
// If so, just use this trait and call it a day.
Some(Pick {
item: probes[0].0.item,
kind: TraitPick,
import_ids: probes[0].0.import_ids.clone(),
autoderefs: 0,
autoref_or_ptr_adjustment: None,
self_ty,
unstable_candidates: vec![],
})
}
/// Similarly to `probe_for_return_type`, this method attempts to find the best matching
/// candidate method where the method name may have been misspelled. Similarly to other
/// edit distance based suggestions, we provide at most one such suggestion.
#[instrument(level = "debug", skip(self))]
pub(crate) fn probe_for_similar_candidate(
&mut self,
) -> Result<Option<ty::AssocItem>, MethodError<'tcx>> {
debug!("probing for method names similar to {:?}", self.method_name);
self.probe(|_| {
let mut pcx = ProbeContext::new(
self.fcx,
self.span,
self.mode,
self.method_name,
self.return_type,
self.orig_steps_var_values,
self.steps,
self.scope_expr_id,
IsSuggestion(true),
);
pcx.allow_similar_names = true;
pcx.assemble_inherent_candidates();
pcx.assemble_extension_candidates_for_all_traits();
let method_names = pcx.candidate_method_names(|_| true);
pcx.allow_similar_names = false;
let applicable_close_candidates: Vec<ty::AssocItem> = method_names
.iter()
.filter_map(|&method_name| {
pcx.reset();
pcx.method_name = Some(method_name);
pcx.assemble_inherent_candidates();
pcx.assemble_extension_candidates_for_all_traits();
pcx.pick_core().and_then(|pick| pick.ok()).map(|pick| pick.item)
})
.collect();
if applicable_close_candidates.is_empty() {
Ok(None)
} else {
let best_name = {
let names = applicable_close_candidates
.iter()
.map(|cand| cand.name)
.collect::<Vec<Symbol>>();
find_best_match_for_name_with_substrings(
&names,
self.method_name.unwrap().name,
None,
)
}
.or_else(|| {
applicable_close_candidates
.iter()
.find(|cand| self.matches_by_doc_alias(cand.def_id))
.map(|cand| cand.name)
});
Ok(best_name.and_then(|best_name| {
applicable_close_candidates.into_iter().find(|method| method.name == best_name)
}))
}
})
}
///////////////////////////////////////////////////////////////////////////
// MISCELLANY
fn has_applicable_self(&self, item: &ty::AssocItem) -> bool {
// "Fast track" -- check for usage of sugar when in method call
// mode.
//
// In Path mode (i.e., resolving a value like `T::next`), consider any
// associated value (i.e., methods, constants) but not types.
match self.mode {
Mode::MethodCall => item.fn_has_self_parameter,
Mode::Path => match item.kind {
ty::AssocKind::Type => false,
ty::AssocKind::Fn | ty::AssocKind::Const => true,
},
}
// FIXME -- check for types that deref to `Self`,
// like `Rc<Self>` and so on.
//
// Note also that the current code will break if this type
// includes any of the type parameters defined on the method
// -- but this could be overcome.
}
fn record_static_candidate(&self, source: CandidateSource) {
self.static_candidates.borrow_mut().push(source);
}
#[instrument(level = "debug", skip(self))]
fn xform_self_ty(
&self,
item: ty::AssocItem,
impl_ty: Ty<'tcx>,
args: GenericArgsRef<'tcx>,
) -> (Ty<'tcx>, Option<Ty<'tcx>>) {
if item.kind == ty::AssocKind::Fn && self.mode == Mode::MethodCall {
let sig = self.xform_method_sig(item.def_id, args);
(sig.inputs()[0], Some(sig.output()))
} else {
(impl_ty, None)
}
}
#[instrument(level = "debug", skip(self))]
fn xform_method_sig(&self, method: DefId, args: GenericArgsRef<'tcx>) -> ty::FnSig<'tcx> {
let fn_sig = self.tcx.fn_sig(method);
debug!(?fn_sig);
assert!(!args.has_escaping_bound_vars());
// It is possible for type parameters or early-bound lifetimes
// to appear in the signature of `self`. The generic parameters
// we are given do not include type/lifetime parameters for the
// method yet. So create fresh variables here for those too,
// if there are any.
let generics = self.tcx.generics_of(method);
assert_eq!(args.len(), generics.parent_count);
let xform_fn_sig = if generics.is_own_empty() {
fn_sig.instantiate(self.tcx, args)
} else {
let args = GenericArgs::for_item(self.tcx, method, |param, _| {
let i = param.index as usize;
if i < args.len() {
args[i]
} else {
match param.kind {
GenericParamDefKind::Lifetime => {
// In general, during probe we erase regions.
self.tcx.lifetimes.re_erased.into()
}
GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
self.var_for_def(self.span, param)
}
}
}
});
fn_sig.instantiate(self.tcx, args)
};
self.tcx.instantiate_bound_regions_with_erased(xform_fn_sig)
}
/// Determine if the given associated item type is relevant in the current context.
fn is_relevant_kind_for_mode(&self, kind: ty::AssocKind) -> bool {
match (self.mode, kind) {
(Mode::MethodCall, ty::AssocKind::Fn) => true,
(Mode::Path, ty::AssocKind::Const | ty::AssocKind::Fn) => true,
_ => false,
}
}
/// Determine if the associated item with the given DefId matches
/// the desired name via a doc alias.
fn matches_by_doc_alias(&self, def_id: DefId) -> bool {
let Some(method) = self.method_name else {
return false;
};
let Some(local_def_id) = def_id.as_local() else {
return false;
};
let hir_id = self.fcx.tcx.local_def_id_to_hir_id(local_def_id);
let attrs = self.fcx.tcx.hir().attrs(hir_id);
for attr in attrs {
if sym::doc == attr.name_or_empty() {
} else if sym::rustc_confusables == attr.name_or_empty() {
let Some(confusables) = attr.meta_item_list() else {
continue;
};
// #[rustc_confusables("foo", "bar"))]
for n in confusables {
if let Some(lit) = n.lit()
&& method.name == lit.symbol
{
return true;
}
}
continue;
} else {
continue;
};
let Some(values) = attr.meta_item_list() else {
continue;
};
for v in values {
if v.name_or_empty() != sym::alias {
continue;
}
if let Some(nested) = v.meta_item_list() {
// #[doc(alias("foo", "bar"))]
for n in nested {
if let Some(lit) = n.lit()
&& method.name == lit.symbol
{
return true;
}
}
} else if let Some(meta) = v.meta_item()
&& let Some(lit) = meta.name_value_literal()
&& method.name == lit.symbol
{
// #[doc(alias = "foo")]
return true;
}
}
}
false
}
/// Finds the method with the appropriate name (or return type, as the case may be). If
/// `allow_similar_names` is set, find methods with close-matching names.
// The length of the returned iterator is nearly always 0 or 1 and this
// method is fairly hot.
fn impl_or_trait_item(&self, def_id: DefId) -> SmallVec<[ty::AssocItem; 1]> {
if let Some(name) = self.method_name {
if self.allow_similar_names {
let max_dist = max(name.as_str().len(), 3) / 3;
self.tcx
.associated_items(def_id)
.in_definition_order()
.filter(|x| {
if !self.is_relevant_kind_for_mode(x.kind) {
return false;
}
if self.matches_by_doc_alias(x.def_id) {
return true;
}
match edit_distance_with_substrings(
name.as_str(),
x.name.as_str(),
max_dist,
) {
Some(d) => d > 0,
None => false,
}
})
.copied()
.collect()
} else {
self.fcx
.associated_value(def_id, name)
.filter(|x| self.is_relevant_kind_for_mode(x.kind))
.map_or_else(SmallVec::new, |x| SmallVec::from_buf([x]))
}
} else {
self.tcx
.associated_items(def_id)
.in_definition_order()
.filter(|x| self.is_relevant_kind_for_mode(x.kind))
.copied()
.collect()
}
}
}
impl<'tcx> Candidate<'tcx> {
fn to_unadjusted_pick(
&self,
self_ty: Ty<'tcx>,
unstable_candidates: Vec<(Candidate<'tcx>, Symbol)>,
) -> Pick<'tcx> {
Pick {
item: self.item,
kind: match self.kind {
InherentImplCandidate(_) => InherentImplPick,
ObjectCandidate(_) => ObjectPick,
TraitCandidate(_) => TraitPick,
WhereClauseCandidate(trait_ref) => {
// Only trait derived from where-clauses should
// appear here, so they should not contain any
// inference variables or other artifacts. This
// means they are safe to put into the
// `WhereClausePick`.
assert!(
!trait_ref.skip_binder().args.has_infer()
&& !trait_ref.skip_binder().args.has_placeholders()
);
WhereClausePick(trait_ref)
}
},
import_ids: self.import_ids.clone(),
autoderefs: 0,
autoref_or_ptr_adjustment: None,
self_ty,
unstable_candidates,
}
}
}